Flexographic printing machines of this type are known, for example, from German Patent [OLS] Nos. 2,941,521, 3,437,216, 3,742,129 and 4,001,735.
For printing machines and, in particular, also for flexographic printing machines, there exists the problem that when the machine is stopped, the ink dries on the inking rolls or on the screen rolls, so that upon restarting and further operation of the machine, difficulties occur. A known means to prevent this problem, is to move the inking rolls or screen rolls away from the size cylinders and to allow them to slowly continue to run, so that drying of the ink on the inking or screen rolls is prevented.
In the case of a known multicolor flexographic printing machine, known from German Patent No. 742,317, the impression rolls as well as the size cylinders assigned to each of the impression rolls and the screen rolls and dampening rolls of the inking devices are driven by a primary central wheel during the normal printing process, which directly meshes with the toothed wheels attached to the one shaft extension of the inking rolls, while the drives of the size cylinders and of the screen rolls and dampening rolls are derived from the toothed wheels wedged onto the other shaft extension. In order to assure continued operation during machine stoppages of the screen rolls and dampening rolls, which have been moved away from the size cylinders, a second central wheel, which can be driven by a servomotor, is provided which drives the meshing toothed drive wheels of the screen rolls and dampening rolls via toothed wheels which are placed in a freely rotatable manner on axle spindles of the impression rolls and the size cylinders, wherein a coupling device is provided which, during machine stoppages, switches the drive of the second central wheel to the servomotor.
However, due to its gear construction, this known continuous operation drive is very costly. Furthermore, even during a size cylinder change, toothed wheels must be exchanged in order to drive the inking device rolls.
For this reason, it is the purpose of the invention to create a simply constructed continuous operation drive for the inking device rolls and, in particular, the screen rolls of printing machines, especially flexographic printing machines.